Gay and bisexual men have been told they cannot take part in blood plasma trials as part of efforts to treat COVID-19 patients because "men who have sex with men are at an increased risk of acquiring certain infections through sex."Doctors are carrying out tests to understand if blood plasma from those who have recovered from COVID-19 can be used to treat other patients who are still ill with the virus.The plasma of survivors contains coronavirus antibodies and it is hoped that patients who are.